Just how deep in the deepest point in the ocean? Here's a handy guide mapping James Cameron's descent to the Challenger Deep back in March.

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On March 25, James Cameron became the third person—and the only one traveling solo—to visit Challenger Deep, 6.8 miles below the western Pacific Ocean's surface. With the help of the Australia-based Acheron Project, the director engineered the Deepsea Challenger, a one-of-a-kind vertical-descent submersible equipped with HD 3D cameras [1], tools to gather scientific samples [2], and specially designed batteries housed in plastic cases filled with silicon oil [3]. Instead of building the sub out of steel and using foam to make it neutrally buoyant, Acheron created a new syntactic foam—epoxy resin containing hollow glass microspheres—that serves as the main structural material [4]. Cameron sat in a 2.5-inch-thick, 43-inch-diameter steel sphere [5], where he controlled the sub with joysticks. Deepsea Challenger reached the bottom in 2.5 hours with the help of 1000-plus pounds of steel weights [6]. Cameron had to resurface after 3 hours on the seafloor because of a hydraulic leak—he flipped a switch to jettison the weights and ascended in 70 minutes—but by and large, the sub performed as planned. "Yeah, your life is at risk any time you go into a hostile environment like that," he told Popular Mechanic last fall. "But you trust the engineering."